Semiconductor device

The disclosure of Japanese Patent Application No. 2022-150352 filed on Sep. 21, 2022, including the specification, drawings and abstract is incorporated herein by reference in its entirety.

The present disclosure relates to a semiconductor device and, more particularly, to a technique applicable to a semiconductor device capable of transmitting signals between different potentials by using a pair of inductors coupled inductively.

There are disclosed techniques listed below.

Patent Document 1 describes a technique capable of increasing the coil cross-sectional area without hindering miniaturization in order to reduce the series resistance which occupies most of the parasitic resistance components of the coils configuring the transformer.

For example, there is a transformer (digital isolator) that enables contactless signal transmission by using a pair of inductors coupled inductively. Since this transformer allows signal transmission in a non-contact state, the electrical noise from one circuit can be suppressed from adversely affecting the other circuit. In addition, in the transformer configured as described above, improvement in the breakdown voltage is desired so as to enable non-contact signal transmission between circuits having large different potentials from each other.

In one embodiment, a semiconductor device includes a lower wiring layer, a multilayer wiring layer formed on the lower wiring layer, and an upper wiring layer formed on the multilayer wiring layer. Here, the lower wiring layer includes a first wiring, the multilayer wiring layer includes a second wiring, and the upper wiring layer includes a third wiring. In this case, the first wiring has a thickness greater than a thickness of the second wiring, and the third wiring has a thickness greater than the thickness of the second wiring. The lower wiring layer includes a lower inductor being a component of a transformer, and the upper wiring layer includes an upper inductor being a component of the transformer.

According to one embodiment, the reliability of the semiconductor device can be improved.

In all the drawings for explaining the embodiments, the same members are denoted by the same reference numerals in principle, and repetitive descriptions thereof are omitted. Note that even plan view may be hatched for the sake of clarity.

Circuit Configuration

is a diagram showing a configuration example of a drive control unit that drives a load circuit such as a motor.

As shown in, the drive control unit includes a control circuit CC, a transformer TR, a transformer TR, a drive circuit DR, and an inverter INV, and is electrically connected to a load circuit LOD.

The drive control unit further includes a transmitting circuit TX, a receiving circuit RX, a transmitting circuit TX, and a receiving circuit RX. The transmitting circuit TXand the receiving circuit RXtransmit a control signal outputted from the control circuit CC to the drive circuit DR. On the other hand, the transmitting circuit TXand the receiving circuit RXtransmit a signal outputted from the drive circuit DR to the control circuit CC. The control circuit CC controls the drive circuit DR. The drive circuit DR operates the inverter INV that controls the load circuit LOD based on the control from the control circuit CC.

A power supply potential VCCis supplied to the control circuit CC, and the control circuit CC is grounded by a ground potential GND. On the other hand, a power supply potential VCCis supplied to the inverter INV, and the inverter INV is grounded by a ground potential GND. For example, the power supply potential VCCsupplied to the control circuit CC is smaller than the power supply potential VCCsupplied to the inverter INV. In other words, the power supply potential VCCsupplied to the inverter INV is larger than the power supply potential VCCsupplied to the control circuit CC.

The transformer TRis formed of a coil (inductor) CLand a coil CLinductively coupled to each other. The inductively coupled coil CLand coil CLare interposed between the transmitting circuit TXand the receiving circuit RX. Thus, it is possible to transmit a signal from the transmitting circuit TXto the receiving circuit RXvia the transformer TR. Consequently, the drive circuit DR can receive the control signal outputted from the control circuit CC via the transformer TR.

As described above, by the transformer TRelectrically isolated by using the inductive coupling, it is possible to transmit the control signal from the control circuit CC to the drive circuit DR while suppressing the transmission of the electric noise from the control circuit CC to the drive circuit DR. Therefore, a malfunction of the drive circuit DR caused by the superimposition of the electric noises on the control signal can be suppressed resulting in improvement on the operation reliability of the semiconductor device.

The coil CLand the coil CLconfiguring the transformer TReach function as an inductor. The transformer TRfunctions as a magnetically coupled element formed of the inductively coupled coil CLand coil CL

Similarly, the transformer TRformed of inductively coupled coil CLand coil CLis interposed between the transmitting circuit TXand the receiving circuit RX. Thus, it is possible to transmit a signal from the transmitting circuit TXto the receiving circuit RXvia the transformer TR. Consequently, the control circuit CC can receive the signal outputted from the drive circuit DR via the transformer TR.

As described above, electrically isolating the transformer TRusing the inductive coupling allows a signal to be transmitted from the control circuit CC to the drive circuit DR while suppressing the transmission of the electric noise from the control circuit CC to the drive circuit DR. Therefore, a malfunction of the drive circuit DR caused by the superimposition of the electric noises on the control signal can be suppressed resulting in improvement on the operation reliability of the semiconductor device.

The transformer TRis configured by the coil CLand the coil CL, and the coil CLand the coil CLare not connected by conductors but are magnetically coupled. Therefore, when a current flows in the coil CL, a change in the current facilitates an induced electromotive force to be generated in the coil CLand an induced current to flow in the coil CL. In this case, the coil CLis a primary coil, and the coil CLis a secondary coil. As described above, the transformer TRutilizes the electromagnetically induced phenomena occurring between the coil CLand the coil CL. That is, as a result of transmitting a control signal from the transmitting circuit TXto the coil CLof the transformer TRto cause a current to flow in the coil CLof the transformer TR, an induced current generated in the coil CLof the transformer TRis detected by the receiving circuit RX, so that the receiving circuit RXcan receive a signal corresponding to the control signal outputted from the transmitting circuit TX.

Similarly, the transformer TRis configured by the coil CLand the coil CL, and the coil CLand the coil CLare not connected by conductors but are magnetically coupled. Therefore, when a current flows in the coil CL, a change in the current facilitates an induced electromotive force to be generated in the coil CL, so that an induced current flows in the coil CL. As described above, as a result of transmitting a signal from the transmitting circuit TXto the coil CLof the transformer TRto cause a current to flow in the coil CLof the transformer TR, the induced current generated in the coil CLof the transformer TRis detected by the receiving circuit RX, so that the receiving circuit RXcan receive a signal corresponding to the control signal outputted from the transmitting circuit TX.

Signals are transmitted and received between the control circuit CC and the drive circuit DR using a path from the transmitting circuit TXto the receiving circuit RXvia the transformer TRand using a path from the transmitting circuit TXto the receiving circuit RXvia the transformer TR. That is, the transmission and reception of the signals between the control circuit CC and the drive circuit DR are performed by having the receiving circuit RXreceive the signal transmitted from the transmitting circuit TXand by having the receiving circuit RXreceive the signal transmitted from the transmitting circuit TX. As described above, the transformer TRis interposed in the transmission of a signal from the transmitting circuit TXto the receiving circuit RX, and the transformer TRis interposed in the transmission of a signal from the transmitting circuit TXto the receiving circuit RX. Thus, the drive circuit DR can drive the inverter INV for operating the load circuit LOD in accordance with the signal transmitted from the control circuit CC.

The control circuit CC and the drive circuit DR have different reference potentials. That is, in the control circuit CC, the reference potential is fixed to the ground potential GND, while the drive circuit DR is electrically connected to the inverter INV as shown in. The inverter INV includes, for example, a high-side IGBT (Insulated Gate Bipolar Transistor) and a low-side IGBT. The drive circuit DR performs the on/off control of the high-side IGBT of the inverter INV and the on/off control of the low-side IGBT of the inverter INV causing the inverter INV to control the load circuit LOD. Specifically, the on/off control of the high-side IGBT is performed by the drive circuit DR controlling the potential applied to the gate electrode of the high-side IGBT. Similarly, the on/off control of the low-side IGBT is performed by the drive circuit DR controlling the potential applied to the gate electrode of the low-side IGBT.

Here, for example, in order to realize the on-control of the low-side IGBT, the drive-circuit DR controls to apply “emitter potential (0 V)+threshold voltage (15 V)” to the gate electrode with reference to the emitter potential (0 V) of the low-side IGBT connected to the ground potential GND. On the other hand, for example, in order to realize the off-control of the low-side IGBT, the drive-circuit DR controls to apply an “emitter potential (0 V)” to the gate electrode with reference to the emitter potential (0 V) of the low-side IGBT connected to the ground potential GND.

Therefore, the on/off control of the low-side IGBT is performed according to whether or not a threshold voltage (15 V) is applied to the gate electrode with 0 V as a reference potential.

On the other hand, for example, the on-control of the high-side IGBT is also performed by whether or not “reference potential+threshold voltage (15 V)” is applied to the gate electrode with respect to the reference potential using the emitter potential of the high-side IGBT as a reference potential.

Unlike the emitter potential of the low-side IGBT, the emitter potential of the high-side IGBT is not fixed to the ground potential GND. That is, in the inverter INV, the high-side IGBT and the low-side IGBT are connected in series between the power supply potential VCCand the ground potential GND. In the inverter INV, when the high-side IGBT is turned on, the low-side IGBT is turned off, and when the high-side IGBT is turned off, the low-side IGBT is turned on. Therefore, since the low-side IGBT is in an on-state when the high-side IGBT is in an off-state, the emitter potential of the high-side IGBT becomes the ground potential GNDdue to the low-side IGBT being in the on-state.

On the other hand, since the low-side IGBT is in off-state when the high-side IGBT is in on-state, the emitter potential of the high-side IGBT becomes an IGBT bus-voltage. In such case, the on/off control of the high-side IGBT is performed by whether or not “reference potential+threshold voltage (15 V)” is applied to the gate electrode with the emitter potential of the high-side IGBT as a reference potential.

As described above, the emitter potential of the high-side IGBT varies depending on whether the high-side IGBT is in the on-state or the off-state. That is, the emitter potential of the high-side IGBT varies from the ground potential GND(0 V) to the power supply potential VCC(for example, 800V). Therefore, in order to turn on the high-side IGBT, an “IGBT bus-voltage (800 V)+threshold voltage (15 V)” needs to be applied to the gate electrode with the emitter potential of the high-side IGBT as a reference potential. Therefore, it is necessary for the drive circuit DR that performs the on/off control of the high-side IGBT to detect the emitter potential of the high-side. Therefore, the drive circuit DR is configured to receive the emitter potential of the high-side IGBT. Consequently, the drive circuit DR receives the reference potential of 800 V, and the drive circuit DR controls the high-side IGBT to be turned on by applying the threshold voltage (15 V) to the gate electrode of the high-side IGBT with respect to the reference potential of 800 V. Therefore, a high potential of the order of 800 V is applied to the drive circuit DR.

As described above, the drive control unit includes the control circuit CC that handles the low potential (several tens of volts) and the drive circuit DR that handles the high potential (several hundreds of volts). Therefore, the signal transmission between the control circuit CC and the drive circuit DR requires the signal transmission between the different potential circuits.

In this regard, the signal transmission between the different potential circuits can be performed by performing the signal transmissions between the control circuit CC and the drive circuit DR via the transformer TRand the transformer TR.

As described above, a large potential difference may be generated between the primary coil and the secondary coil of each of the transformer TRand the transformer TR. Conversely, since a large potential difference may occur between the primary coil and the secondary coil, the primary coil and the secondary coil are magnetically coupled instead of being connected by a conductor to transmit signals. Therefore, when forming the transformer TR, it is important to increase the breakdown voltage between the coil CLand the coil CLas much as possible from the viewpoint of improving the operation reliability of the semiconductor device. Similarly, when forming the transformer TR, it is important to increase the breakdown voltage between the coil CLand the coil CLas much as possible from the viewpoint of improving the operation reliability of the semiconductor device.

is an explanatory diagram showing a transmission example of the signal.

In, the transmitting circuit TXextracts an edge part of a signal SGof the square wave inputted to the transmitting circuit TX, generates a signal SGhaving a constant pulse width, and transmits the signal SGto the coil CL(primary coil) of the transformer TR. When the current caused by the signal SGflows to the coil CL(primary coil) of the transformer TR, a signal SGcorresponding to the current flows to the coil CL(secondary coil) of the transformer TRby the induced electromotive force. The receiving circuit RXamplifies the signal SGand further modulate the signal SGinto a square wave, such that the receiving circuit RXoutput a signal SGof the square wave. Thus, the signal SGcorresponding to the signal SGinputted to the transmitting circuit TXcan be outputted from the receiving circuit RX. In this way, it is possible to transmit the signal from the transmitting circuit TXto the receiving circuit RX. The signal transmission from the transmitting circuit TXto the receiving circuit RXcan likewise be carried out.

Two-Chip Configuration

The transmitting/receiving circuits of the above-described drive control unit are formed, for example, by dividing into two semiconductor chips. Specifically,is a diagram showing a two-chip configuration. In, the two-chip configuration includes a semiconductor chip CHPand a semiconductor chip CHP. The semiconductor chip CHPincludes the transmitting circuit TX, the transformer TR, and the receiving circuit RX. On the other hand, the semiconductor chip CHPincludes the receiving circuit RX, the drive circuit DR, the transmitting circuit TX, and the transformer TR. In such a two-chip configuration, for example, the transformer TRis formed on the same semiconductor chip CHPas the transmitting circuit TXand the receiving circuit RX. Therefore, the transformer TR, the transmitting circuit TX, and the receiving circuit RXcan be integrated. Similarly, the transformer TRis formed on the same semiconductor chip CHPas the drive circuit DR, the receiving circuit RX, and the transmitting circuit TX. Therefore, the transformer TR, the drive circuit DR, the receiving circuit RX, and the transmitting circuit TXcan be integrated.

However, in the two-chip configuration, for example, since the transformer TR, the transmitting circuit TX, and the receiving circuit RXneed to be formed on one semiconductor chip, a manufacturing process of the semiconductor chip CHPbecomes complicated. Similarly, in the 2-chip configuration, for example, since the transformer TR, the drive circuit DR, the receiving circuit RX, and the transmitting circuit TXneed to be formed on one semiconductor chip, a manufacturing process of the semiconductor chip CHPbecomes complicated. These complications increase the manufacturing costs of the semiconductor chip CHPand the semiconductor chip CHP.

Three-Chip Configuration

Therefore, it has been studied to realize the above-described transmitting and receiving circuit unit with a three-chip configuration instead of the two-chip configuration. Hereinafter, a novel three-chip configuration will be described.

is a diagram showing the 3-chip configuration. In, The three-chip configuration includes a semiconductor chip CHP, a semiconductor chip CHP, and a semiconductor chip CHP. The semiconductor chip CHPincludes the transmitting circuit TXand the receiving circuit RX. In addition, the semiconductor chip CHPincludes the drive circuit DR, the receiving circuit RX, and the transmitting circuit TX. On the other hand, the semiconductor chip CHPincludes the transformer TRand the transformer TR.

Thus, in the three-chip configuration, only the transformer TRand the transformer TRare formed on the semiconductor chip CHP. That is, in the three-chip configuration, the semiconductor chip CHPcan be used if the configurations of the semiconductor chip CHPand the semiconductor chip CHPchange. As a result, the three-chip configuration increases the usable variation of the semiconductor chip CHPand the semiconductor chip CHP. In other words, the versatility of the semiconductor chip CHPon which the transformer TRand the transformer TRare formed can be improved. Further, since the semiconductor chip CHPon which the transformer TRand the transformer TRare formed does not include a transistor, the semiconductor chip CHPcan be formed only by wiring process, and thus, the manufacturing process of the semiconductor chip CHPcan be simplified. Therefore, according to the three-chip configuration, the manufacturing cost of the semiconductor chip CHPcan be reduced, and thus, a highly competitive product can be manufactured.

Planar Layout Configuration of Semiconductor Chip

Subsequently, the planar layout configuration of the semiconductor chip CHPis explained.

is a plan view showing a planar layout configuration of the semiconductor chip CHP.

In, a planar shape of the semiconductor chip CHPhas a rectangular shape. The semiconductor chip CHPincludes a seal ring SR at a peripheral edge portion of the semiconductor chip CHP. In plan view, the semiconductor chip CHPincludes an upper inductorand an upper inductorboth being surrounded by the seal ring SR. Here, the upper inductorhas a tap-pad, a spiral wiringconnected to the tap-pad, and a trans-padconnected to the spiral wiring. Similarly, the upper inductorhas a tap-pad, a spiral wiringconnected to the tap-pad, and a trans-padconnected to the spiral wiring

Further, in plan view, the semiconductor chip CHPincludes a tap-pad, a trans-pad, a tap-pad, and a trans-padall being surrounded by the seal ring SR. The tap-padand the trans-padact as a tap-pad and a trans-pad of a lower inductor (not shown) formed below the upper inductor. That is, the lower inductor that is paired with the upper inductoris formed below the upper inductor, and the tap-padand the trans-paddrawn from the lower inductor via wiring are formed in the same layer as the upper inductor.

Similarly, the tap-padand the trans-padact as a tap-pad and a trans-pad of a lower inductor (not shown) formed below the upper inductor. That is, the lower inductor that is paired with the upper inductoris formed below the upper inductor, and the tap-padand the trans-paddrawn from the lower inductor via wiring are formed in the same layer as the upper inductor.

Here, for example, a high-side reference potential of about 800 V is applied to the upper inductorand the upper inductor. On the other hand, a low-side reference potential of about 0 V is applied to the lower inductor (the tap-padand the trans-pad) and the lower inductor (the tap-padand the trans-pad). That is, a reference potential different from the reference potential applied to the upper inductoris applied to the lower inductor that is paired with the upper inductor. Similarly, a low-side reference potential different from the high-side reference potential applied to the upper inductoris applied to the lower inductor paired with the upper inductor.

Cross-Sectional Structure of Semiconductor Chip

Next, the cross-sectional structure of the semiconductor chip CHPis explained.

is a cross-sectional view of the semiconductor chip CHPalong A-A line of.